This pattern was developed for huge trout at the Lac Holt Lodge in Canada, but smallmouth bass don't know that.
The combination of a sparse deer hair head and silver ribbing help this fly to get a fairly good sink rate in current.
Hook: 4XL streamer, size 4
Thread: 6/0 olive
Tail: A clump of chartruese Glo-Bug yarn
Body: Olive yarn
Ribbing: Silver wire
Wing: Olive chickabou or marabou
Head/collar: Olive deer hair, spun, sparsely packed, and trimmed
It's possible to tie this fly with two different threads. The 6/0 can be used to tie in everything but the deer hair, then 3/0 can be used for the head and collar. If you really like to lean into your deer hair, then this might be a good option. I stay with the 6/0 all the way through the pattern simply because the hair doesn't need to be packed too tightly.